I've actually slept nicely on an airplane; even resting the eyes are good for the muscles and the overall health of the traveler.
I typically listen to music I recognize while I attempt to sleep, regardless of where on the plane I am (even next to the engine). I prefer a window-seat, and I try to secure one as much as possible! Just listen to the music, close your eyes, and focus on the tones until it becomes white noise and you pass out.